XPS study of oxygen interaction with a Ge-covered Si(100) surface

Abstract

The interaction of oxygen with a Ge-covered Si(100)-2 × 1 surface has been studied by X-ray photoelectron spectroscopy (XPS). We have found that oxygen exposure at 300 K leads to oxidation of the Ge overlayer, with a larger population of the higher oxidation states, as compared with oxidized Ge(111) and Ge(100). Our XPS data show that upon mild annealing the oxygen initially bonded to Ge is transferred to Si. The onset of this process is shifted to higher temperatures with increasing Ge coverage, θ Ge. At 800 K all the oxygen atoms are transferred to Si. The oxygen exposure at this temperature leads to oxidation of Si alone, with a rate higher than that of Ge-free Si surfaces.